Normally, when an internal combustion engine, or thermal engine, is started, the electrical starting device passes through three successive phases, namely a driving phase, a freewheeling phase during which the thermal engine turns independently, and a stop phase.
In order to provide the driving and freewheeling phases, there is known in the prior art a starting device comprising an electric motor, an output shaft able to transmit a rotation movement to the thermal engine and a starter-head assembly comprising in particular a freewheel, for example with a roller.
During the driving phase, the electric motor drives the starter-head assembly, which, by virtue of a locking of the freewheel on the output shaft, transmits a rotation movement to the output shaft. The locking of the freewheel on the output shaft causes high contact forces applied locally to this output shaft.
It is also known how to produce a single-piece output shaft comprising a track to which the high contact forces are applied, a support and a pinion intended to drive the thermal engine. The elements of the output shaft may have the same hardness.
However, different elements of the output shaft do not need to have equal hardnesses. In particular, the support does not need to have a hardness equal to the hardness of the track and to the hardness of the pinion.
In this case, in order to satisfy the conditions of local hardness on the output shaft, the output shaft may under go complex heat treatments expensive to implement, for example hardening applied locally to this output shaft.
There therefore exists a need to adapt the hardnesses of the different elements of the output shaft according to their use without having recourse to complex and expensive local heat treatments of the type described above.